Automatic control



Sept@ 10, m46; c. E KETERAN@ 2,407,555

AUTOMATIC CONTROL Filed July so, 194s 2 sheets-shew 1 Cittornegs c. F. KETTERING 294079555 AUTOMATIC CONTROL Sept E0, i945.

Filed July 30, 1945 Z'Sheets-Sheet 2 hmentor Patented Sept. 10, 1946 AUTOMATIC CONTROL Charles F. Kettering, Detroit, Mich., assgnor to General Motors Corporation, Detroit, Mich., a

corporation of Delaware Application July 30, 1943, Serial No. 496,824

'20 Claims.

This invention relates to control, means, and more specifically to automatic steering control means for mobile bodies.

In the operation of mobile bodies, such as aircraft and ships, it is advantageous to be able to set control means'to maintain the body on a given course and so relieve the pilot or helmsman of the tedious task of keeping the body on the course except for occasional checking. In mobile bodies such las torpedoes, either air or water, adapted to explode upon reaching some determined objective, automatic `steering of the same is of course a necessity as no manual `means could be present.

It is therefore an object of my invention to provide means for automatically maintaining a mobile body on a given predetermined course.

It is a further object of my invention to provide automatic steering means for a moving body.

It is a still further objectl of my invention to provide compass-controlled automatic steering means for a mobile body.

With these and other objects in view which will 4become apparent as the specification proceeds, the embodiments of my invention are best understood by reference to the following specification and claims and the illustrations in the `accompanying drawings, in which:

Figure 1 is a schematic wiring diagram of a control system embodying my invention;

Figure 2 is a perspective schematic diagram of the parts and inter-connections of my control system; and

Figure '3 is an enlarged sectional view through the potentiometer and its control.

.Referring now more specifically to Figure 2 of the drawings, it will be seen that the actuating control means for my system is a compass 2 pivotally mounted on a gimbaled ring 3 on a support 4 and arcuately movable between two fixed stops 6 and .8. In its movement the `compass needle intercepts a light beam flowing to photocell I (Fig. l) to vary the output thereof. The support 4 may be rotated about the axis ofthe compass by worm wheel 12 which is rigidly secured to said support and is so mounted asl to be engaged by Worm I4. The latter is connected to one end of a flexible drive shaft I6, the opposite end of which is attached'to and driven by a motor IB. The purpose of this drive means is to provide a follow-up to prevent over-travel or over-correction in the direction of drive control of the compass.

To the shaft 2d of the motor I8 is also secured a pinion `2i. which drives shaft 24 through reduction gears 26 .28 and 30, the latter being mounted on shaft 24 and the two former on an intermediet wheel 34 and at a spaced axial ate coupling shaft 32. Shaft 24 also has a sprockpoint a worm 36, both being rigidly secured'to said shaft. Worm 36 is adapted to engage a worm wheel 38 which is connected by a link mechanism 40 with a steering rudder 42 for the craft being driven. A steering shaft 44, which is adapted to cooperate with some type of steering wheel 46 or similar steering mechanism, is mounted in a portion of the frame 48 of the body and has thereon a second sprocket wheel 5U and also a small pinion 52. A drive chain 54 is adapted to run over the two sprocket wheels 50 and 34 and 'to cause a driving connection between the two. Thus when the steering wheel 4t is turned, the rudder 42 will rotate and steer the mobile body.

Pinion 52 is adapted to engage a gear 5G mounted on a short rotatable stub shaft 58, the opposite end of which carries a small bevel gear 6E! which forms part of the differential incorporating two rotatable bevel gears 52 and t4 both engaging the bevel gear (il) at diametrically opposite points, and supported by suitable means such as pins (i5 from the surface of a large gear wheel 58, said gear wheel 68 being mounted upon shaft 1i! but freely rotatable with respect thereto. Shaft 'lo also carries at its extreme end a bevel gear 1.2 which meshes with the two bevel gears 62 and 64 to Complete the differential. A small worm 14 is mounted to contact the teeth of the worm wheel E8, said worm being driven by a small trim motor 16.

Mounted upon the opposite end of the shaft 1U to that upon which gear 'l2 is mounted is a radially extending contact arm 13 electrically insulated therefrom which is adapted to engage a circular resistor mounted in an insulating housing 82 and to form therewith a variable potentiometer for purposes to be described. Mounted in housing 82-at a greater radial distance from the potentiometer resistance are two arcuate rings 84 and 85, each of which extends substantially but are separated slightly from each other by a portion of the insulating housing. An adjustable insulating collar 8B mounted on the shaft '.'il carries a bowed radially extending arm Sii which is adapted to contact and move over these contact arcs S4 and 36. The electrical connections t0 these arms are made through slip rings V8| and 83.

In order to provide compensation for certain compass movements, which will be described more in detailat a later point, it is necessary to provide a damping or compensating coil such as that vshown at 92 which is mounted on the side of the casing enclosing the needle and which operates in a manner similar to the follow-up means.

Referring now to Figure 1, there is shown the compass 2 controlling the flow of light to the photocell I0 and having mounted near one end thereof the compensating coil 92 which is shown in dotted lines mechanically, but which appears in the electrical circuit in the lower right-hand corner of the circuit diagram between the two resistors in line with the variable potentiometer tap. The photocell I0 is connected through lines 94 and 96 to a suitable amplifier 98, the output of which is connected into a relay coil I 00 which operates a movable armature |02 between two limit positions. This movable armature |02 carries two spaced contacts |04 and |06 insulated from each other, which cooperates with two spaced pairs of stationary contacts |08 and H0 on one side and I I2 and I I4 on the opposite side. Contacts |08 and ||0 are connected to a suitable source of current through lines ||6 and |20, while contacts 2 and ||4 are reversely connected to these same lines through inter-connecting lines |22 and |24. Contact |04 is connected through line |26 to one side of a steering motor I8 and also to resistor |28. Contact |06, on the other hand, is connected through line |30 to the opposite terminal of motor I8 and also to a resistor |32.

Potentiometer coil 80 has one end connected to line |34 which is also connected to one of the conductor arcs 84 and to one terminal of a battery |36. The opposite end of the battery |36 is connected to line |38 which terminates in switch |40, the opposite terminal of which is connected through line |42 to one terminal of the trim motor 16, this latter motor being geared to the control shaft carrying the control arms 00 and 18. The opposite terminal of the motor 'I6 is .i

connected to line |44 which in turn is connected to said rotatable arm 90. This arm cooperates with the two arcuate sections 84 and 86. Section 86 is connected through line |46 to the opposite end of potentiometer 80 and to one terminal of a battery |48 whose opposite terminal is connected to line |38 and battery |36, placing the two batteries in series. Two resistors |50 and |52 are connected in series across the two batteries. A resistor |54 is connected to the midpoint of these two resistors and also to line |56 which extends to resistor |28 and one terminal of the compensating coil 92. The movable contact I8 of the potentiometer 80 is connected to line |58 which terminates in resistor |60 whose opposite terminal is connected to resistor |32 and coil 92.

In the operation of the device, the control motor I8, which is a reversible motor and can be rotated in either direction, depending upon the polarity of the current applied thereto, turns, through obvious connections, the rudder to steer the mobile vehicle, and at the same time turns the rotatable housing in which the compass is mounted to provide follow-up means. The control for this motor I8 is through the photocell I0 which in turn is energized by the amount of light falling thereon, determined by the inter,- ception of said light by the position of the compass needle. The output of the phototube is amplified and the amplified result is in turn applied to the relay roil |00. Thus, if the needle swings to one side and allows considerable light to fall onto the photocell, enough current will be provided to the relay coil |00 to cause it to attract its armature |02 and raise it up until contacts |04 and |06 engage contacts |08 and ||0 respectively. This connects the motor I8 to the input lines I I6 and |20 and the motor I8 rotates, turning the rudder 42 to cause the course of the mobile body to be altered slightly. At the same time, through motor energization, the casing or housing 4 for the compass is so rotated as to cause the compass needle to tend to assume a neutral position again with respect to this housing. 'Ihus only small impulses of steering are applied to the rudder.

If now the compass assumes such a position as to intercept considerable light and the output of the photocell falls', the energy provided to the relay coil |00 will not be sufficient to maintain the armature in its uppermost position, and it will fall so that contacts |84 and |06 now engage contacts ||2 and I|4 and in so doing reverse the polarity of the current flowing to the motor I8 which therefore causes it to rotate in the opposite direction and move the rudder 42 alsoin the opposite direction. This also turns the followup mechanism to drive the housing 4 back to try to align the compass therewith. l

Coil 92 has previously been referred to as a compensating and damping coil andits functions and operation will now be described in detail. It is a well-known fact that when compass means is tilted in any manner so that its axis is not ver tical, the vertical component of the earths eld introduces a magnetic force acting on the compass, which provides an erroneous indication or operation as the case may be. In the present instance the compass needle 2 is pivotally mounted on a vertical axis within a horizontally trunnioned gimbal ring 3. The bottom of the ring is slightly heavier than the top and so the assembly tends to remain in a. vertical position, irrespective of thev rolling or tossing of the mobile body. When, however, the body turns, then the centrifugal force causes the girnbal ring to move out of its vertical position and therefore the vertical axis of the compass is now moved to a slantmg position. The vertical component of the earths eld will now tend to rotate the compass needle to give an erroneous reading and one of the functions of the coil is to compensate for this force.

It will also be evident that the sharper the turn, the greater will be the centrifugal force and more will be the displacement and the vertical pull on the compass and therefore the restoring or compensating force must be stronger. I have provided means therefore for so controlling the iield of the compensating coil that the latter varies dependent upon the displacement of the rudder. In other words, if the rudder is forced hard over, the body will execute a Shar-p turn, the centrifugal force will be large, and a large compensating eld will be necessary. This proportional control is provided by the balanced potentiometer 10--80 and its associated circuit which provides to compensating coil 92 current from the batteries |36, |48 proportional to the rudder displacement 'and L so poled as to repel the tendency of the needle to be attracted by the vertical component of the earths eld. It should also be fpointed'out that this error is more prevalent when the body is set on a north course since any deviation therefrom will tilt the vertical axis of the needle in such a plane that the vertical component of the earths field has maximum effect. It is therefore termed the north course error. The effect of this bias'- ing magnetic force upon the needle which is proportional to rudder displacement also acts asl a magnetic follow-up device and tends to align the needle with the photocell light source to balance the same.

It will be seen by referring to Figure 1 that there are two sources of power for coil 92. The first is from batteries |38 and |48 which are connected through potentiometer f8-89 to coil 92. When the former is balanced, no current flows through the coil, but when it is unbalanced, then current will flow through the coil in a direction dependent upon which way the arm 18 Vmoves from the center and proportional to the amount of .displacement of the arm which is driven synchronously with the rudder. Therefore whichever side of neutral the rudder is moved, .a biasing magnetic field will be appliedto the compass needle to tend to push lit back to neutral, the strength of the field being proportional to the rudder displacement.

It will be noted that there are two lines, namely, |216 and I'Bil, which extend from the power supply for the steering motor I8 and are connected across the co-il 92 through resistors |28 and |32 to provide the second source. The effect of this source of power is much less than that provided by the batteries and balanced potentiometer, but it does also provide ya magnetic biasing field which tends to move the compass needle in the opposite direction from that in which the earths eld is moving it to damp the needle movement and give it a force in the opposite direction where needle movement causes the relay switch Illll to be actuated. Therefore, as the body tends to :move off course, the needle will swing to one side, calling for corrective rudder, and the relay lswitch IUD will be actuated to drive motor I8 to move the rudder. Current will be applied to coil B2 from lines |26 and it, creating a magnetic field to tend to force the needle back to its neutral position to prevent excessive swing. At the same time, the motor turns the compass housing to provide mechanical follow-up for the same purpose. Further magnetic field is provided by coil 9,2 as the rudder moves away from neutral by the simultaneous movement of the potentiometer ,i

arm 18, which field, as previously described, provides correction for the north turning error proportional to rudder displacement,

From the above it will be obvious that when the ship or craft is moving along its normal course,

the potentiometer must normally be set at balanced position. If, therefore, a new course is set and the craft is turned through operation of the manual steering wheel, the potentiometer will become unbalanced and the relation between the compass housing and potentiometer changed. Therefore, after the new course has been ascertained, and the craft has been properly aligned, in order to again balance the potentiometer and regain proper relation to the control compass, switch lai! is closed which completes the circuit to the trim motor 15. The rotatable arm 90 and the arcuate conducting discs 86 and 84 on member 82 control the trim motor, and a circuit is therefore completed to this motor whose polarity and therefore the direction of rotation of the motor will depend upon whether the rotatable arm Si) is engaging arcuate member 84 or 8E. Assuming that the arm 90 engages member 86 Gil as shown in the circuit diagram, the motor circuit r will be completed as follows: motor 16, line |44, arm 90, arcuate conductor B6, line |46, battery |48, line |38, switch lll-.0, line |42, back to .the motor 16. This causes the worm 14 to be roworm drives the worm wheel 68 vwhich carries the two bevel gears 62 and 64 of the differential. Since at this particular instant shaft 44 is locked, due to the fact that the rudder is in correct position and so Vheld or locked for the moment, bevel gear 6,0 will not rotate and the rotation of the worm wheel 68 .will be transmitted through gears 82 .and 'S4 to gear 12 and therefore rotatethe shaft iil. This in turn moves arm 1B of the lpotentiometer and this will approach its balanced condition. The `motor circuit will be broken when arm Bil reaches a point. between the .two arcs 8d and 85 which consists of insulating material of the member B2i It will be noted Athat there are vtwo of lthese positions at 1,80" apart. Thus, lwhen the motor circuit is broken by arm til riding off the conductive member, the Vpotentiometer will lagain be balanced and the system adjusted.

VI claim;

'1. In a control system for a mobile body, steering means for the body, magnetic .means responsive to the earths terrestrial field controlling the steering means, current conducting means. for creating a magnetic field mounted in juxtaposition to the magnetic means, a source of power therefor and adjustable means connected between the source of power and said conducting means controlling the flow of current to the latter and therefore the strength of the magnetic field created thereby.

2. In a control system for a mobile body, steering means for the body, magnetic means responsive to the earths terrestrial field controlling Athe steering means, current conducting means for creating a magnetic eld mounted in juxtaposition to ,the magnetic means, a source of power therefor, adjustable means connected between the source of power and said conducting means controlling the flow of current to the latter and therefore the strength of the magnetic field created thereby, and means interconnecting the adjustable means with the steering means so the two will operate in .synchronism and the magnetic field generated will be proportional to the displacement of the steering means.

3. In a control system for a mobile body, steering means for the body, compass means for controlling the steering means, a coil for creating a modifying magnetic field mounted adjacentl the compass, a source of power for the coil, and reversing and varying means for the current connected between the .source and the coil for varying the effect of the latter on said compass.

4. In a control system'for a mobile body, steerling'means for the body, compass means for controlling the steering means, a coil for creating a modifying magnetic eld mounted adjacent the compass, a source of power for the coil,'r'eversing `and varying means for the current connected between the source and the coil for varying the effect of the latter on said compass, and means interconnecting said steering means and said reversing :and varying means whereby the effect of the coil is determined by the position of the steer'- -ing means.

5.. In a control system for a mobile body, `steering means for the body, compass means for controlling the steering means, a coil for creating a modifying magnetic field mounted adjacent the compass, a source of power for the coil, balanced potentiometer means connected between the source of power and coil and means interconnecting the potentiometer and the steering means tated in a given direction. The rotation of this Iii whereby as the latter is moved from its center position, current of one polarity or the other will be applied to the coil and increased in proportion to the deflection of said steering means.

6. In a control system for a mobile body, steering means for the body, compass means for controlling the steering means, a coil for creating a modifying magnetic field mounted adjacent the compass, a source of power for the coil, balanced potentiometer means connected between the source of power and coil, means interconnecting thepotentiometer and the steering means Whereby as the latter is moved from its center position, current of one polarity or the other will be applied to the coil and increased in proportion to the deflection of said steering means, driving means differentially connected into the interconnection between the steering means and the potentiometer, means connecting the driving means to the source of power and switching means between the source and the driving means actuated by the movement of the interconnecting means to bring the potentiometer to balanced position.

7. In a control system for a mobile body, steering means for the body, reversible driving means for turning the latter in either direction, reversing switching means controlling the driving means, compass means connected to and operating the switching means, a coil mounted in juxtaposition to the compass means and connected across the driving means whereby as the polarity of the current to the driving means is reversed, the current flow through the coil will also be reversed and the eifect of the coils magnetic held on the compass will likewise be reversed.

8. In a control system for a mobile body, steering means for the body, reversible driving means for turning t .e latter in either direction, reversing switching means controlling the driving means, compass means connected to and operating the switching means, a coil mounted in juxtaposition to the compass means and connected across the driving means whereby as the polarity of the current to the driving means lis reversed, the current flow through' the coil will also be reversed and the effect of the coils magnetic field on the compass will likewise be reversed, a separate source of power, and a balanced potentiometer connected thereto and to the coil whereby .any unbalance of the potentiometer will cause additional bias voltage to be applied to the coil which may aid or oppose the first voltage to modify the effect thereof.

9. In a control system for a mobile body, steering means for the body, reversible driving means for turning the latter in` either direction, reversing switching means controlling the driving means, compass means connected to and operating the switch means, a coil mounted in juxtaposition to the compass means and connected across the driving means whereby as the polarity of the current to the driving means is reversed, the vcurrent now through the coil will also be reversed and the'eifect of the coils magnetic field on the compass will likewise be reversed, a separate source of power, a balanced potentiometer connected thereto and to the coil whereby any unbalance of the potentiometer will cause additional bias voltage to be applied to the coil which may aid or oppose the viirst voltage to modify the effect thereof, and movable means for varying the setting on the potentiometer driven by the driving means.

l0. In a control system for a mobile body,

reversing switching means controlling the driving means, compass means connected to and operating the switching means, a coil mounted in juxtaposition to the compass means and connected across the driving means whereby as the polarity of the current to the driving means is reversed, the current now through the coil will also be reversed and the eifect of the coils magnetic eld on the compass will likewise be reversed, a, separate source of power; a balanced potentiometer connected thereto and to the coil whereby any unbalance of the potentiometer will cause additional bias voltage to be applied to the coil which may aid or oppose the first voltage to modify the effect thereof, movable means for varying the setting on the potentiometer driven by the driving means, and a second driving means for returning the 'potentiometer to balanced condition when energized.

11. In a control system for a mobile body, steering means for the body, a reversible driving motor connected to said steering means, a source of power, reversing switching means connected to the source and motor to control the same, compass means to actuate the switching means, a coil mounted adjacent the compass means to create a biasing neld therefor and connected to the reversing switching means whereby it will be energized simultaneously with the motor.

12. In a control system for a mobile body, steering means for the body, a reversible driving motor connected to said steering means, a, source of power, reversing switching means connected to the source and motor to control the same, compass means to actuate the switching means, a coil mounted adjacent the compass means to create a biasing field therefor and connected to the reversing switching means whereby it will be energized simultaneously with the motor, a separate source of power, a resistance connected across said source, a movable contact engaging said resistor and connected to said coil, means connecting said coil to the second source of power whereby when the circuit is balanced, no current flows through the coil from the separate source, but when unbalanced, current may flow in either direction, depending upon the direction of unbalance.

13. In a control system for a mobile body, steering means for the body, a reversible driving motor connected to said steering means, a source of power, reversing switching means connected to the source and motor to control the same, compass means to actuate the switching means, a coil mounted adjacent the compass means to create a biasing eld therefor and connected to the reversing switching means whereby it will be energized simultaneously with the motor, a separate source of power, a resistance connected across said source, a movable contact engaging said resistor and connected to said coil, means Connecting 'said coil to the second source of power whereby when the circuit is balanced, no current ilows through lthe coil from the separate source, but when unbalanced, current may flow in either direction, depending upon the direction of unbalance, and means interconnecting the steering means and the movable contact to cause them to move together to apply an additional biasing force to the compass means, dependent upon the position of the steering means.

14. In a control system for a mobile body, steering means for the body, a reversible driving motor connected to said steering means, a source of power, reversing switching means connected to the source and motor to control the same, compass means to actuate the switching means, a

sistor and connected to said coil, means connectl ing said coil to the second source of power whereby when the circuit is balanced, no current ows through the coil from the separate source, but when unbalanced, current may flow in either direction, depending upon the direction of unbal. a

ance, means interconnecting the steering means and the movable contact to cause them to move together to apply an additional biasing force to the compass means, dependent upon the position of the steering means, a second driving motor, and interconnecting means between this second motor and the movable contact to provide for driving said movable contact to balanced position without moving said steering means.

l5. In a control system, steering means, means including compass means controlling the steering means, and means for creating a magnetic eld in the vicinity of the compass means energizable simultaneously with the steering means to create a repulsive force in an opposite direction to that in which the compass tends to move due to the terrestrial iield.

16. In a control system, compass means, means controlled thereby to steer a, mobile body on a predetermined course and magnetic biasing means in juxtaposition to the compass means energized from the control means to create a magnetic field to tend to cause the compass to move in a direction opposite from that in which the terrestrial. eld tends to move it.

17. In a control system, steering means, reversible driving means connected to lsaid steering means for turning thelatter in either direction, pivotal compass means controlling the driving means and means for creating a magnetic eld in the vicinity of said compass to bias the same connected to said driving means and energized simultaneously therewith. n

18. In a control systemv for a mobile body, steering means for the body, reversible driving means for turning the latter inl either direction, compass means, switching means controlled by the compass meansl to actuate the driving means, means for creating a biasing magnetic iield in the vicinity of the compass means connected to and energized simultaneously with the driving means to damp the movement of :the compass.

19. In a control system'for a mobile body, steering means for the body, reversible driving means for turning the latter in either direction, compass means, switching means controlled by the compass means to actuate the driving means, means for creating a biasing magnetic eld in the vicinity of the compass means connected to and energized simultaneously with the driving means and an additional source of adjustable power connected to the magnetic means to supplement the power supplied thereto from the driving means.

20. In a control system for a mobile body, steering means for the body, reversible driving means for turning the latter in either direction, compass means, switching means controlled by the compass means to actuate the driving means, means for creating a biasing magnetic field in the vicinity of the compass means connected to and energized simultaneously with the driving means, an additional source of adjustable power connected to the magnetic means to supplement the power supplied thereto from the driving means, and means for adjusting the value of the last-named power means actuated by the driving means.

CHARLES F. KE'I'I'ERING. 

